The invention relates generally of an internal-gear machine such as an internal-gear pump.
Generally, in an internal-gear machine of that kind, such as a pump, an externally toothed pinion or pump impeller is mounted eccentrically with respect to the body of the pump to actuate an internally toothed annular gear which rotates in the casing of the pump. Flow through the pump is practically continuous and without reversals and high rotary speeds may be used. To obtain the desired function, a filler member is disposed in the clearance between the internally and externally toothed gears. Thus, German laid-open application (DE-OS) No. 29 42 417 discloses an internal-gear machine which comprises a casing with an internally toothed annular gear mounted rotatably therein. An externally toothed pinion meshes with the teeth of the annular gear and a generally sickle-shaped filling member is disposed in the clearance between the gears. The filling member is divided along a generally circumferentially extending surface into first and second portions, the end faces of which bear against a support surface provided by a support pin member extending axially through the clearance between the gears. That arrangement provides that the filling member portions are displaceable in a radial direction against the support surface of the supportpin member and can also perform a pivotal movement about the longitudinal axis thereof, by virtue of the support pin member being mounted rotatably. That provides that the portions of the filling member can be in substantially sealing relationship against the tips of the associated gears, even in the event of relative movements, wear and the like occurring. However, the rotatable mounting of the support pin member must be of a high degree of precision in order to attain the desired purpose; if that were not the case, the support pin member and/or the filling member bearing thereagainst would not be properly guided in the casing of the pump and could not perform the necessary movements to compensate for wear and the like. Furthermore, the support pin member, in order to provide a satisfactory support and guidance effect, must be mounted at both ends with a high degree of precision and that in turn means that the walls of the casing in which the support pin member is carried, that is to say, first and second casing portions which are disposed in opposite relationship in the assembled condition to define the space within which the internally toothed annular gear rotates, must be aligned relative to each other with a very high degree of accuracy and joined together in that aligned relationship. If the casing portions are not properly aligned, then the support member will be unable to perform a satisfactory pivotal movement to enable the filling member to perform its function. Such precision in turn requires a substantial level of expenditure in regard to manufacture and assembly, and that in turn results in the overall price of the machine being increased.